Plutonium is a member of the actinide group in the periodic table. Plutonium atoms have 94 electrons and 94 protons with 2 valence electrons in the outer shell. There are 150 neutrons in the most abundant isotope.

Characteristics and Properties

Under standard conditions plutonium is a hard, brittle, silvery metal. It is a poor conductor of electricity and heat. When exposed to air, it becomes covered in a dark gray layer of oxidation.

All forms of plutonium are radioactive and decay to other elements over time. Most isotopes decay to uranium.

Plutonium-239 is one of the main fissile elements. Fissile means that it can sustain a chain reaction of nuclear fission. This characteristic is important in nuclear reactors and nuclear explosives.

Where is it found on Earth?

Plutonium is an extremely rare element in the Earth's crust. It is so rare that for many years it was thought that it did not occur naturally. The main source of plutonium is from the use of uranium-238 in nuclear reactors. Large quantities are produced each year by this process.

How is plutonium used today?

Plutonium is used in both nuclear reactors and nuclear weapons. It was used to create the second nuclear weapon deployed during World War II which was the "Fat Man" nuclear bomb dropped on Nagasaki, Japan.

Plutonium has also been used as a power and heat source for spacecraft. It was used on the Voyager and Pioneer space probes as well as the Pathfinder Mars robot lander and the Curiosity Mars rover.

How was it discovered?

Plutonium was discovered by a team of scientists at the Berkeley Radiation Laboratory in California in 1940. Glen Seaborg, Arthur Wahl, Edwin McMillan, and Joseph Kennedy produced and isolated plutonium-238 from a sample of uranium. The discovery of plutonium was kept secret until 1946 because of World War II.

Where did plutonium get its name?

It was named after the dwarf planet Pluto (which was considered a full planet at the time). This followed from the tradition started when uranium was named after the planet Uranus.

Isotopes

Plutonium does not exist in nature and has no known stable isotopes. The longest-lived isotope is plutonium-244 which has a half-life of just over 80 million years.

Interesting Facts about Plutonium

It can form up to seven different allotropes (crystal structures).

Famous scientist Enrico Fermi claimed he discovered element 94 in 1934, but it turned out to be a mixture of other elements including barium and krypton.

It was once thought that plutonium did not exist in nature, but trace amounts have been found in uranium ores.

The first production of plutonium was at the Oak Ridge National Laboratory in Tennessee. It was made for the Manhattan Project to make a nuclear bomb.

It was once used to power pacemaker batteries, but has since been replaced.